A number of different techniques are previously known for separating thin-walled thermoformed articles from sheets of thermoformable plastic material. Typically, articles are trimmed from a sheet or web of material and an article ejector is utilized along with co-acting male and female trim dies to advance articles from between the co-acting dies after they have been severed from the sheet or web of material.
A typical thermoforming operation molds articles into a heated material web, such as a sheet of solid or foamed-plastic material. The heated web of material is transported to a thermoforming machine where the articles are formed in the web. The web is then transported from the thermoforming machine at a relatively high operating speed into a trim press where the articles are severed from the web of material. Typically, the trim press includes article ejectors that assist in removing the articles from the web of material and from between a pair of co-acting dies, after severing from the web.
U.S. Pat. No. 4,391,171 discloses a trim press with an article ejector that is mounted on a moving die assembly to separate severed articles from a moving trim die. More particularly, the article ejector is mechanically driven by a drive mechanism comprising a flywheel that also drives the trim press dies. The flywheel drives a rocker arm assembly to-and-fro via a connecting rod to move an ejector plate and ejector pins. However, such a construction uses a series of complicated mechanical linkages which substantially increase the weight of moving components. Furthermore, such a construction utilizes the same flywheel drive mechanism to move the die platens and dies, as well as to move the article ejector. Because the same mechanical drive mechanism is used for driving both components, there is very little time in which to activate the article ejector during a cyclical trim operation. The articles need to be ejected after a trim operation has been implemented, but before a web of material is fed for a subsequent trim operation. Accordingly, there is only a small period of time in a cycle of operation between successive trim operations in order to eject articles. Such limited time means that it is often only possible to run 50 to 60 cycles during a trim operation. Furthermore, the mechanical components are frequently lubricated. Because the mechanical components need to move at an extremely high rate of speed (due to the limited amount of time in which to implement the operation), there is a risk that lubricating grease and oil will become airborne or thrown about which can contaminate articles that are being severed for use in the food industry.
U.S. Pat. No. 5,199,340 illustrates an ejector mechanism having ejector pins moveable relative to a die member via a longitudinally extending ejector bar driven by a trip lever via a toggle linkage mechanism. This ejector mechanism is similar to the previously cited article ejector in that oscillating components are utilized to drive the ejector mechanism, and the main drive mechanism for a trim press is also utilized to drive the ejector mechanism. Hence, the previously recited problems also are encountered by this ejector mechanism.
Accordingly, improvements are needed to overcome the previously recited problems. Furthermore, a smaller overall package size is also desired for an article ejector to accommodate mounting onto trim presses having limited available mounting space for an article ejector.